1. Field of Invention
Embodiments of the present invention relate generally to a system and a method for supporting a web in a polishing system.
2. Background of Invention
One type of polishing material that includes abrasives disposed therein is known as fixed abrasive material. The fixed abrasive material comprises a plurality of abrasive particles suspended in a resin binder that is disposed in discrete elements on a backing sheet. As the abrasive particles are contained in the polishing material itself, systems utilizing fixed abrasive material generally use polishing fluid that do not contain abrasives. Such polishing fluids enhance the service life of their fluid delivery systems.
Fixed abrasive polishing material is generally available in stickdown form but is often utilized in the form of a web. Generally, the web is periodically advanced over the course of polishing a number of substrates as the polishing surface of the web is consumed by the polishing process. A vacuum is typically applied between the web and platen to fix the web to the platen during the polishing process. When the web is advanced, the vacuum is removed, freeing the web from the platen's surface.
However, indexing the web across a polishing platen is sometimes difficult. Fluids that come in contact with the web may cause surface tension or attraction to develop between the web and the underlying surface of the platen. This surface tension must be over-come to accomplish advancement of the web. If the attraction between the web and platen is great, the indexing means may not be able to index the web or the web may become damaged during the indexing process.
Providing a cushion of gas between the web and platen assists in overcoming the attraction between the web and platen. The gas lifts the web to a spaced-apart relation to the platen where the web may be freely indexed. However, providing gas to the area between the web and platen is complicated, and requires rotary union and process tubing to be routed through an already crowded platen.
Therefore, there is a need for an improved apparatus that supports a web of polishing material.